ColumnSet: Fix horizontal scrollbar regression on IE8
ColumnSet: Fix horizontal scrollbar regression on IE8

Also remove a space that was added to a query selector in
_onColumnSetScroll, which inexplicably causes acme to crash IE8

kfranqueiro/dgrid,dylans/dgrid,maier49/dgrid,maier49/dgrid,dylans/dgrid,kfranqueiro/dgrid,kfranqueiro/dgrid,maier49/dgrid,dylans/dgrid